What Does the Emerald Ash Borer Look Like? A Quick Identification Guide

The emerald ash borer (EAB) is an invasive, wood-boring beetle that has made its way to North America, posing a significant threat to ash trees throughout the continent. Understanding what this pest looks like is essential for identifying infestations and taking steps to protect our valuable ash trees.

Adult EABs have a distinctive appearance, with a shiny emerald green body and a coppery red or purple abdomen. They are small, measuring approximately ⅜ to ⅝ inch long, and leave unique D-shaped exit holes in the bark of the branches and trunk of infested trees.

By familiarizing yourself with the emerald ash borer’s appearance, you’ll be equipped to recognize signs of infestation and more effectively safeguard the ash trees in your area.

Identifying the Emerald Ash Borer

Physical Appearance

The Emerald Ash Borer is a metallic green beetle with a flattened body. Its vibrant color can make it easy to spot on ash trees.


The size of these beetles is relatively small. Adult Emerald Ash Borers are typically ½-inch long and ⅛-inch wide, which is almost the size of President Lincoln’s image on a penny.

Distinctive Features

Here are some distinct features of Emerald Ash Borers:

  • Color: The metallic green color of these beetles is distinct and can help with easy identification.
  • Size: As mentioned earlier, their small size (similar to President Lincoln’s image on a penny) is another unique feature.
  • Flat body: Their flattened body separates them from many other beetle species.

In conclusion, the Emerald Ash Borer’s distinctive features like metallic green color, small size, and flattened body make it easily identifiable as a pest on ash trees. Remember to always observe responsibly and keep an eye out for these invasive insects to protect your ash trees.

Life Cycle of the Emerald Ash Borer

Egg Stage

In the egg stage, female Emerald Ash Borers lay numerous eggs in bark crevices and layers. The eggs usually hatch within 7-10 days.

Larvae Stage

After hatching, the larvae bore into the tree, where they chew the inner bark and phloem. They leave behind winding galleries as they feed, which end up cutting off the flow of water and nutrients in the tree. Larvae go through four stages of development, leading to significant damage to the affected trees.

Pupa Stage

Following the larval development, the Emerald Ash Borer enters the pupa stage, where it remains inside the tree, preparing to transform into an adult.

Adult Stage

Eventually, adult Emerald Ash Borers emerge, typically during the months of May to July. These beetles are responsible for the continuation of their lifecycle, as they mate and lay eggs on ash trees, causing further damage and tree mortality.

Infestation Signs

Symptoms on Ash Trees

When emerald ash borer infestations occur, there are several symptoms you may notice on ash trees. Firstly, leaves at the top of ash trees may begin to wilt, and you might see gradual dieback in the canopy of the tree. Additionally, the tree may produce new sprouts along the lower trunk and bark splits.

D-Shaped Exit Holes

One of the most distinctive signs of emerald ash borer infestation is the presence of D-shaped exit holes. Adult emerald ash borers leave these holes behind when they emerge from the tree in June and July. These holes are approximately 1/8″ wide, and the flat side can face any direction.

Bark Splits and Galleries

As the emerald ash borer larvae feed beneath the bark, they create galleries, which are winding tunnels they excavate while consuming the tree’s tissues. These galleries disrupt the flow of nutrients within the tree and cause bark splits. You may also notice frass, which is a combination of sawdust and insect waste found near the galleries.

To sum up, be on the lookout for wilted leaves, dieback in the canopy, new sprouts along the trunk, D-shaped exit holes, bark splits, and galleries when trying to identify an emerald ash borer infestation. Remember, early detection is crucial in managing the infestation and protecting your ash trees.

Impact on Ash Trees

Nutrient and Water Uptake

The emerald ash borer (EAB) has a significant impact on the nutrient and water uptake of ash trees. When EAB larvae feed on the tree’s inner bark and disrupt the flow of nutrients and water, the tree gradually weakens1. You may notice that the canopy of an infected tree starts to thin out and eventually die because of reduced nutrient and water supply.

Tree Health and Mortality

EAB infestations pose a severe threat to the health and survival of ash trees. As the tree’s ability to transport nutrients and water is compromised, its overall health declines2.The mortality rate of infected ash trees is alarmingly high – EAB has killed tens of millions of ash trees in the United States alone3. Some factors contribute to the mortality of ash trees due to EAB:

  • Rapid spread of EAB
  • Difficulty in early detection of infestations
  • Lack of effective prevention methods

Bark and Leaves Impact

EAB infestations can cause visible changes in the bark and leaves of ash trees. As the larvae feed underneath the bark, they create serpentine-like galleries that disrupt the tree’s vascular system. This can cause the bark to crack and split, exposing the tunnels4. Furthermore, EAB-infested trees often display symptoms such as:

  • Yellowing and wilting of leaves
  • Premature leaf drop
  • Sparse or no foliage in the canopy

By keeping an eye on the health of your ash trees and looking out for these symptoms, you can detect EAB infestations early and take appropriate action to save your trees.

Spread of the Emerald Ash Borer

Natural Spread

The emerald ash borer is an invasive species of beetle that originates from Asia and is primarily responsible for the destruction of ash trees in North America. The beetle spreads naturally through their natural flight and mating patterns. Adult beetles are known to fly up to several miles in search of suitable ash trees for laying their eggs. When the eggs hatch, the larvae feed on the tree’s inner bark, eventually killing the tree. As a result, ash tree populations have been significantly impacted by these beetles.

Human-Related Spread

In addition to natural spread, human activities also contribute to the dispersal of emerald ash borers. One of the main factors is the transportation of infested firewood. People often unknowingly move firewood from infested areas to non-infested regions, providing new hosts for the beetles to infest. It is important to be aware of local regulations and quarantine zones to help prevent the spread of these invasive beetles. In fact, there are numerous efforts in place to control the spread of emerald ash borers, such as:

  • Restricting the movement of ash firewood, logs, and nursery stock
  • Monitoring and early detection using trapping methods
  • Developing biological control measures, such as introducing natural predators like parasitoid wasps
  • Encouraging responsible firewood use by using local sources or heat-treated firewood

By understanding the implications of the emerald ash borer’s natural and human-related spread, you can play a part in minimizing the damage caused by these invasive beetles on ash trees in your area. Always be cautious about the origin of your firewood and stay informed about local regulations and quarantine measures.

Protection and Management


Monitoring is crucial for early detection and management of emerald ash borer infestations. You can help by regularly inspecting your ash trees for signs of damage, such as:

  • Splitting bark
  • Thinning crown
  • Unusual woodpecker activity

If you suspect an infestation, report it to your local forestry agency or extension office.

Pesticides and Biological Controls

Strategies for controlling emerald ash borer include pesticides and biological controls. Effective pesticide options include imidacloprid, which can be applied to the soil around the affected tree. When using pesticides, follow all label instructions and consult with a certified arborist.

Biological controls involve releasing natural predators of the emerald ash borer, such as parasitic wasps, to help manage populations. These efforts are still under research and might not be available for widespread use yet.

Community Involvement

Collaborating with your community is essential to managing emerald ash borer infestations effectively. Here are some ways you can get involved:

  • Spread awareness about emerald ash borer and its impact on ash trees
  • Attend community meetings or workshops focused on emerald ash borer management
  • Support local ordinances that encourage responsible tree maintenance and disposal

By working together, we can protect our ash trees from this invasive pest and preserve the health of our forests.

Impact on Different Ash Species

Black Ash

Black ash trees are highly susceptible to the emerald ash borer (EAB), which could cause severe damage and eventually kill the tree. EAB larvae feed on the tissues under the tree’s bark, weakening it and causing the tree to die. Some examples of potential damage include:

  • Canopy dieback
  • Bark splitting
  • Increased woodpecker activity

Green Ash

Green ash trees are commonly planted across the United States and are vulnerable to EAB attacks. The beetle attacks and kills green ash trees by eating the tissues under the bark, leading to similar damages as those experienced by black ash trees.

White Ash

White ash trees, including the popular ‘Autumn Purple’ cultivar, are also susceptible to EAB infestations. The invasive insect causes damage and death to these trees, similar to the effects on black and green ash trees.

Blue Ash

Blue ash trees are relatively resistant to EAB, although they may still become infested. These trees possess a unique bark structure that makes it more difficult for EAB to establish a feeding site. This resistance helps protect blue ash trees from extensive damage caused by the beetle.

European Ash

European ash trees are currently not native to the United States, and their susceptibility to EAB is unknown. However, given the invasive beetle’s destruction of other ash species, it is possible that European ash trees could be vulnerable if introduced to areas where EAB is present.

In summary, EAB poses a significant threat to various ash species, with black, green, and white ash trees being particularly susceptible. Blue ash trees exhibit a higher resistance, while the vulnerability of European ash trees remains uncertain.

Geographical Presence

Native Habitat

The Emerald Ash Borer (EAB) is native to several regions in Asia, specifically countries like China, Mongolia, North Korea, South Korea, Japan, Taiwan, and the Russian Far East. In its native habitat, this insect thrives in various climates and feeds on ash trees.

Global Invasion

Unfortunately, the EAB has also invaded other parts of the world. In 2002, it was first detected in the United States. Since then, it has caused significant damage to ash trees in affected areas.

In the United States, the Emerald Ash Borer has spread to multiple states, including Colorado. This invasive species poses a severe threat to ash tree populations, both native and non-native.

Characteristics of the Emerald Ash Borer

To help you identify EAB, here are its key features:

  • Iridescent green and copper color
  • Bullet-shaped body, typical of buprestid beetles
  • Size: approximately 0.5 inches (1.27 centimeters) long and 0.13 inches (0.32 centimeters) wide

The presence of EAB can also be detected through the following signs:

  • D-shaped exit holes in the bark of infested ash trees
  • Winding galleries under the bark, filled with frass (insect excrement)
  • Thinning or dying foliage

In conclusion, it’s essential to stay vigilant and monitor your ash trees, as early detection could help manage the spread of this destructive pest.


  1. Emerald Ash Borer Signs and Symptoms

  2. Emerald Ash Borer Frequently Asked Questions

  3. The impact of emerald ash borer | Illinois Extension

  4. Emerald Ash Borer | NDSU Agriculture

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Banded Ash Borer


Subject:  What bug is this
Geographic location of the bug:  Southeast pennsylvania
Date: 03/25/2018
Time: 07:50 PM EDT
Your letter to the bugman:  I think this is an ash borer. We only see it when we bring ash firewood into the house. Can you tell exactly what borer it is. Pics are of the back and the belly sides. Thanks
How you want your letter signed:  Dalton

Banded Ash Borer

Dear Dalton,
Thank you for resending the images.  This is a Banded Ash Borer,
Neoclytus caprea, and according to BugGuide:  “often emerges indoors from firewood; sawlogs may become infested within 20 days of felling during summer.” 

Banded Ash Borer
Thank you for the clarification. The room they are in has 1” pine on walls and 5/16 pine on ceiling and solid larch beams.  all has urathane on the front and is kiln dried except for beams. But after 12 years of the wood burner in this room I would think they are pretty dry also.
Any chance of these critters infesting wood in the room. ????
Oops. Sorry. Just looked at the various info you sent and have answer my own questions. Thanks very much for getting back. I searched every bug guide I could find online and never found a pic of them.
We highly doubt that would happen.

Letter 2 – Possibly Banded Ash Borer


Black and Yellow Striped Beetle
Location:  Southern Utah
July 31, 2010 5:52 pm
I live in Hurricane, Utah, and we went down to the Kolob Reservoir earlier today to fish, and I caught this bug. It looks to me like a Yellow and Black Striped Beetle of some sort. I thought it was a bee at first because of the markings, but it doesn’t have a stinger. It also spreads its wings, but doesn’t seem to fly.

Banded Ash Borer, we believe

Hi Beau,
The angle of view of your photograph is not ideal for identification purposes as it doesn’t fully illustrate the banding pattern on the wings of your beetle which is classified as a Longhorned Borer Beetle in the family Cerambycidae.  We are relatively certain it is in the tribe Clytini, but there are several genera and species with very similar markings.  Based on your location, we favor this being a Banded Ash Borer,
Neoclytus caprea, which is profiled on BugGuide.  The coloration and pattern is quite similar to several wasps, and it is believe to be a wasp mimic with protective coloration.

Letter 3 – Possibly Banded Ash Borer


Subject:  What’s this bug
Geographic location of the bug:  Pittsburg, KS
Date: 02/28/2018
Time: 06:34 PM EDT
Your letter to the bugman:  These bugs are in our living room.  New to us.  We have a wood stove but they seem to be on the couch in front of wood stove.
How you want your letter signed:  Sherry Blatchley

Banded Ash Borer

Hi Sherry,
This is definitely the adult of wood boring grubs in the family Cerambycidae, and it looks to us like a Banded Ash Borer,
Neoclytus caprea, based on images posted to BugGuide.  That determined, the wood from your wood burning stove is a likely source of their appearance.  Though they will emerge from firewood, they will not reproduce in the milled lumber in your home or its furnishings. 

Mr. Marlos, 
Thank you so much for your quick response.
We really appreciate the information and have learned a valuable lesson.  Even though we’ve used a wood stove without confronting bugs in the house, all wood will stay outside  until ready to put in the stove!
Thank you for this service that you do,
Sherry Blatchley 



  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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